Study On Preparation Of Modified SiO₂ Composite Sol And Superhydrophobic Surface Of Cotton Fabrics

With the development of the textile industry and the improvement of people’s living standard, people’s idea of wearing apparel also has significant changes. People has higher and higher requirement for the quality of textiles, especially for environmental and functional textiles. In recent years, nano-silica is widely used to fabricate superhydrophobic textiles. As the combination between nano-silica and fabric mainly was physical adsorption, after washing many times, nano-silica attached on the surface of the fabric was easy to fall off, leading to poor washing fastness, which limitied the application of nano-silcia on textiles. Therefore, it is very important to enhance the binding force between the nano-silica and fabrics to improve combining fastness and prepare superhydrophobic functional textiles with good washability.To solve these problems, cotton fiber was modified by citric acid, and the modified Si O2 composite sol was prepared to fabricate superhydrophobic surface of cotton. Also, the hydrophobicity, durability and surface morphology of the treated fabrics were researched. The major studies included:(1)The modified nano-silica was prepared by sol-gol method. The influence of reaction conditions on the modified nano-silica was discussed. The results showed that the modified nano-silica sol with good dispersibility could be obtained at 30℃, when the concentration of tetraethyl orthosilicate(TEOS) was 3%, the concentration of γ-amino propyl trimethoxy silane(APTMS) was 2% and the amnonia amount was 2m L. The prepared modified nano-silica had narrow size distribution with an average particle diameter of 65.88 nm and polydispersity index(PDI) of 0.096. Modified nano-silica sol was stable and transparent, FT-IR spectra showed that the functional amino group was successfully introduced onto the macromolecular chains of nano-silica.(2)Hydrophobic cotton fabrics were successfully obtained via two-step process by the incorporation of A-Si O2 sol and subsequent hydrophobization with 3% hexadecyltrimethoxysilane(HDTMS). The different influence factors on hydrophobic effect of treated cotton were analyzed. The cotton fabrics treated by two-step process exhibited excellent water repellency with the water contact angle(CA) of 150.36°, the shedding angle(SHA) of 12° and water repellence rating of 70. The SEM analysis showed that the fiber surface were obviously covered by a great number of particles to fabricate microscale rough structures, realizing hydrophobic. Furthermore, the more uniform size distribution and the smaller PDI of A-Si O2 sol particle contributed to the hydrophobic effect. With the increase of HDTMS or stearic acid concentration, hydrophobicity of the treated cotton was improved. When the baking temperature was 120 ℃ and baking time was 60 min, the treated cotton fiber showed good water repellence effect. In addition, two-step hydrophobic finishing had less impact on the cotton fabrics’ rigid-flexible, whiteness, breaking strength and the other mechanical properties.(3)To further improve the the combination between cotton fiber and Si O2 sol, cotton fiber surface was modified by citric acid and modified Si O2 composite sol was prepared based on A-Si O2 sol. The modified Si O2 composite sols were applied to the modified cotton fabrics by one-step process. More covalent binding between the –OH、-NH2 on the particles and –OH 、 –COOH on the surface of cotton occurred, and the prepared superhydrophobic cotton had good durability. The results showed that, the modified cotton fabrics treated by modified Si O2 composite sol exhibited excellent superhydrophobicity, with a water contact angle of 155.26°, a shedding angle of 8° and water repellence rating of 100. In addition, after 20 washing cycles, the treated superhydrophobic cotton fabric still had water repellency, with a water contact angle of 143.37°, a shedding angle of 25° and water repellence rating of 70. Compared with the unmodified cotton fabric, SEM analysis showed that the cotton fabric modified by citric acid had rougher surface and higher static contact angle. After washing many times, the treated cotton had a better durability as the hydrophobic membrane on surface of the treated cotton was not easy to break or fall off. Superhydrophobic cotton fabrics by one-step finishing also had less impact on its physical and mechanical properties.